My guess is that Rothbard's motivation wasa) The paleos were/are right about foreign interventionism, and opposition to non-defensive war is the #1 libertarian issue.b) The paleos were/are right about safeguarding national sovereignty - not because national sovereignty is so great, but because it's a safeguard against fraudulent "free trade" agreements and social engineering from the UN and other international organizations.c) The paleos were/are right about "states rights" as opposed to federal court meddling, because an out-of-control judiciary does not really safeguard liberty, but only opens the door for the rest of the federal government to be out-of-control. Moreover, secession fits in well with libertarian principles.d)The paleos were/are the most reliable allies in the struggle for lower taxes and a smaller federal government.

In terms of policy, then, paleo-conservatives were more than 50% in agreement. I further speculate Rothbard believed that, through men like Ron Paul, paleoconservatives could then be brought along, albeit gradually, to a more libertarian philosophy.

Of course, this strategy won't make sense to self-described libertarians who would destroy other countries to "liberate" them, who believe the federal courts should be involved in every question from abortion to prayer in school, and/or whose conception of "free markets" means pro-Wall Street policies and a competent Fed chief. To such folks, the paleo-conservatives are the enemy. In their view, aligning with people who are uncomfortable with, say, gay marriage, is unpardonable, whereas slaughtering civilians of nations that do not attack us is entirely appropriate, or at least a "reasonable" position within libertarianism.

And this is why such self-described libertarians despise Ron Paul so much. He's actually united large numbers of libertarian and paleoconservatives, and in their eyes this will set the libertarian movement back.

There may be a valid criticism of this alliance and of Ron Paul. It has been made by anti-voting anarchists and Libertarian Party die-hards. But it doesn't carry much weight when made by "pro-war libertarians," because they are not part of the libertarian movement. If the libertarian movement is not, at its core, an anti-war movement, then it doesn't really exist.